MADRID (Reuters) - Real Madrid captain and goalkeeper Iker Casillas has rallied behind Jose Mourinho after the Portuguese coach was whistled by some home fans during a King's Cup match at the Bernabeu on Tuesday.

The split over Mourinho, under pressure after his side slipped 11 points behind leaders and arch rivals Barcelona in La Liga, was evident as some supporters whistled when others chanted his name in a 3-0 second-leg win against third-tier Alcoyano that sent Real through to the last 16 7-1 on aggregate.

"I think a couple of months ago the people that were whistling yesterday were the people who were clapping and cheering when we won the league," Casillas said at a promotional event in Madrid on Wednesday.

"Memories are short in football and maybe people do not remember who led the team to win the record breaking league title: most goals, most points," added the Spain international.

"We must also remember the good times and the continuity in this project, which started a long time ago, with a very young team that has been improving.

"We've won the King's Cup, La Liga, the (Spanish) Super Cup. This team does not want to stop and wants to achieve more."

Mourinho has a chance to win over more of the club's demanding fans when city neighbours Atletico Madrid visit the Bernabeu in La Liga on Saturday.